Gloss is an important quality criterion for assessing the quality of paints, coatings, plastic surfaces and the like. Measuring gloss with results that are repeatable and precise is, however, exceptionally difficult. In its general definition, gloss is the property of a surface regarding its ability to reflect light. The more complex the shape, the more difficult it is to accurately measure gloss. Adding to the complications, the light used to measure gloss is itself imprecise. The characteristics of light render the intensity of the reflected light subject to variations due to voltage or frequency changes, as well as localized moisture or other atmospheric conditions. The physical dimensions of a sample combined with the inconsistent intensity of the light sources make it difficult to standardize gloss measurements across samples. As well, considerable physical deviations within a sample make it difficult to standardize the results of gloss measurements.
Photo-spectrometers are known and widely used in various technical disciplines. Commonly owned U.S. Published Patent Application No. 2009/031649, which is hereby incorporated by reference, describes a ring shaped spectrophotometer for use in measuring the color of a sample. Spectrophotometers are used for the purposes of measuring and calibrating various sample colors and hues. Similarly, gloss meters are likewise standard components of color sampling and measuring devices. Both of these devices are commonly combined to provide general color and gloss measuring functions. In both devices, light is reflected off the surface and is measured and recorded with optical sensors. Optical sensors have improved fidelity and reliability over human observation; however, the precision of the current art devices is in need of improvement.
Conventional gloss-meters and gloss-measurement devices suffer from a number of inherent drawbacks. Many of these drawbacks are the result of technical limitations due to component selection and orientation of both light sources and sensors. In fact, most of the mechanisms for determining the gloss of an object are quite limited in their mechanical operation.
There are drawbacks when using conventional gloss measuring devices. U.S. Published Patent Application US 2009/0316149 to Ingleson, which is hereby incorporated by reference, provides a spectral measurement device that includes a gloss measurement option. The reference provides for a spectrometer using a 45°/0° or sphere based color measurement instrument, while including a separate 60° gloss measurement channel. This measurement channel is separated from the main spectral measurement devices. Additionally, the gloss measurement device can only be operated while the spectral device is not engaged. Furthermore, Ingleson fails to compensate for the inherent variability in the light source.
U.S. Pat. No. 5,401,977 to Schwarz, which is hereby incorporated by reference, is directed to a manual measurement of a gloss sample designed to achieve a suitable compensation factor. That apparatus and system is not configured to use a reference channel to automatically calibrate the sample using a light channel of a spectrophotometer. Additionally, the Schwarz reference fails to compensate for thermal and other drifts in the light source.
U.S. Pat. No. 5,377,000 to Berends, which is hereby incorporated by reference, is directed to a gloss measurement system that uses signal value compensation to correct for errors in the measurement. The device of Berends is limited to using two light sources at opposite ends of the visible wavelength spectrum.
U.S. Pat. No. 6,233,053 to Preston, herein incorporated by reference, is directed to a dual function gloss measurement device. The device of Preston is limited to using multiple light sources to provide corrected gloss values to a measurement device.
These deficiencies in the prior art render the ability to measure gloss difficult and inconsistent. Therefore, what is needed in the art is an integrated gloss measurement device and spectrophotometer that provides improved gloss measurement results. What is also needed in the art is such a system and apparatus that also simplifies and standardizes gloss measurements. What is further needed is such a system and apparatus that is capable of engaging gloss and color sensors concurrently in determining on a gloss value of a sample.